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SteveDeFacto

OpenGL PrtScn is black in full screen?

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When I try to capture a screen shot of my program in full screen all I get is a black image. I set the pixel format on my window like this:


[code]
int pixelFormat;
UINT numFormats;
float fAttributes[] = {0,0};

int iAttributes[] =
{
WGL_DRAW_TO_WINDOW_ARB, GL_TRUE,
WGL_SUPPORT_OPENGL_ARB, GL_TRUE,
WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
WGL_COLOR_BITS_ARB, 24,
WGL_ALPHA_BITS_ARB, 0,
WGL_DEPTH_BITS_ARB, 0,
WGL_STENCIL_BITS_ARB, 0,
WGL_DOUBLE_BUFFER_ARB, GL_TRUE,
0, 0
};
wglChoosePixelFormatARB( instance->hDC, iAttributes, fAttributes, 1, &pixelFormat, &numFormats);
SetPixelFormat( instance->hDC, pixelFormat, NULL );[/code]


I go to full screen like this:


[code]
SetWindowLong(hWnd, GWL_STYLE, WS_POPUP);
RECT Rect;
GetWindowRect(hWnd, &Rect);
DEVMODE dmScreenSettings = {0};
dmScreenSettings.dmSize = sizeof(dmScreenSettings);
dmScreenSettings.dmPelsWidth = Rect.right;
dmScreenSettings.dmPelsHeight = Rect.bottom;
dmScreenSettings.dmBitsPerPel = 24;
dmScreenSettings.dmFields = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;
ChangeDisplaySettings( &dmScreenSettings, CDS_FULLSCREEN );
ShowWindow( hWnd, SW_SHOW );
SetFocus(hWnd);[/code]


Any idea why capturing the screen with PrtScn would not work on my program?

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Not really sure but alot of games give me a black screen when trying to use print screen in full screen. You could perhaps handle the print screen key press yourself, render a frame and copy it to the clipboard.

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[quote name='Nanoha' timestamp='1313589903' post='4850322']
Not really sure but alot of games give me a black screen when trying to use print screen in full screen. You could perhaps handle the print screen key press yourself, render a frame and copy it to the clipboard.
[/quote]

Not an awful idea though I would like to make that my last resort in case it's just some random setting I can change to get it to work.

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Hey Steve, I have this problem too and i use glutEnterGameMode to get there. I'd like to leave it up to the host OS too, if possible. I encounter this in all display modes (actually i only tried 16, 24 and 32 bit, various refresh rates and resolutions). This might not be of much help, sorry for getting your hopes up. :-/

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I had even weirder problems with fullscreen print screen. Occasionally it was okay, but sometimes it copied a screen that was overwritten long ago... (a noob loadscreen). Maybe some triple-buffering is going on.

You could also try Alt+PrintScreen (interestingly, a lot of people don't know this. This prints only the active window.)

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I always wondered since when PrintScreen gives a black screen in games, Vista/7 only maybe? Using fraps works great, and some games have their own "print screen" button which generate a bitmap/jpg in the game folder. Guess you have to do custom code for it now, when it was working great in the XP days.Back then, only movies (in windows media player and such) gave black screens.

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I also have this problem (win7). To solve it I either go to windowed mode and use print screen or use my own screen capture and save the context to the HDD. [url="http://freeimage.sourceforge.net/"]Freeimage[/url] is pretty good image library if you are in need of one, can save PNGs.

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Hi guys, either this won't work, or we are just sloppy at searching altogether:
[url="http://msdn.microsoft.com/en-us/library/dd318295(v=vs.85).aspx"]http://msdn.microsof...5(v=vs.85).aspx[/url] (Clipboard unsupported through OpenGL for Windows)
[url="http://www.codeguru.com/cpp/g-m/opengl/article.php/c2711"]http://www.codeguru....ticle.php/c2711[/url] (Copying bitmap to clipboard)

... so apparently clipboard is not supported in the official gl for windows. :-(
Maybe it'll come with an update sometime...

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[quote name='SuperVGA' timestamp='1313617344' post='4850489']
Hi guys, either this won't work, or we are just sloppy at searching altogether:
[url="http://www.codeguru.com/cpp/g-m/opengl/article.php/c2711"]http://www.codeguru....ticle.php/c2711[/url]
[url="http://msdn.microsoft.com/en-us/library/dd318295(v=vs.85"]http://msdn.microsof...d318295(v=vs.85[/url]).aspx

... so apparently clipboard is not supported in the official gl for windows. :-(
Maybe it'll come with an update sometime...
[/quote]

That answers the question! Good job finding it!

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